Inhibitory effects and spectral interactions of isomeric methoxyindazoles on recombinant nitric oxide synthases.

A series of isomeric methoxyindazoles has been evaluated as inhibitors of purified recombinant neuronal, inducible, and endothelial nitric oxide synthases (NOS). 7-Methoxyindazole (7-MI) was the most active compound of this series and displayed selectivity toward the constitutive neuronal (NOS I) and endothelial (NOS III) NOS isoforms, the inducible NOS II being almost insensitive to this inhibitor. 6-, 5-, and 4-Methoxyindazoles were almost inactive against all three NOS isoforms.

Enantioselective Sulfoxidation Catalyzed by Vanadium Haloperoxidases.

Vanadium haloperoxidases catalyze the oxidation of halides by hydrogen peroxide to produce hypohalous acid. We demonstrate that these enzymes also slowly mediate the enantioselective oxidation of organic sulfides (methyl phenyl sulfide, methyl p-tolyl sulfide, and 1-methoxy-4 (methylthio)benzene) to the corresponding sulfoxides (turnover frequency 1 min(-)(1)). The vanadium bromoperoxidase from the brown seaweed Ascophyllum nodosum converts methyl phenyl sulfide to the (R)-enantiomer of the sulfoxide (55% yield and 85% enantiomeric excess (ee)).

Enantioselective epoxidation and carbon-carbon bond cleavage catalyzed by Coprinus cinereus peroxidase and myeloperoxidase.

We demonstrate that myeloperoxidase (MPO) and Coprinus cinereus peroxidase (CiP) catalyze the enantioselective epoxidation of styrene and a number of substituted derivatives with a reasonable enantiomeric excess (up to 80%) and in a moderate yield. Three major differences with respect to the chloroperoxidase from Caldariomyces fumago (CPO) are observed in the reactivity of MPO and CiP toward styrene derivatives. First, in contrast to CPO, MPO and CiP produced the (S)-isomers of the epoxides in enantiomeric excess.

The sulphoxidation of thioanisole catalysed by lactoperoxidase and Coprinus cinereus peroxidase: evidence for an oxygen-rebound mechanism.

Using both stopped-flow and conventional spectroscopy, the oxygenation of methyl phenyl sulphide by both lactoperoxidase (LPO) and Coprinus cinereus peroxidase (CiP) was monitored. Controlled continuous addition of H2O2 during turnover and monitoring the presence of native enzymes, compounds I, II and III, led to formation of the sulphoxide in high yield and enantioselectivity. Under those conditions, LPO catalysed the formation of (R) methyl phenyl sulphoxide with a yield of 85% and an enantiomeric excess (e.